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Before You Begin
The worksheet asks you to complete four test tube setups using snails and Elodea with Bromthymol Blue solution. Review the objective before you start: determine which organism combinations produce or consume carbon dioxide based on the color change of the indicator solution.
Step 1: Click the orange "Get Form Now" button at the top of the page to open the worksheet in the editor.
Step 2: After you open the lab form, find the editing tools in the top menu. Use these to type in text fields, mark checkboxes, and complete each section of the worksheet.
Enter your hypothesis and the required details in each field of the PDF lab worksheet.
In the "Draw the picture" area and the CO2 indicator color fields, record whether the Bromthymol Blue changed color for each test tube. A yellow color indicates CO2 is present. A blue or green color means CO2 is low or absent.
Complete the Hypothesis field and the "Explain how carbon dioxide cycles" and "If I add a snail and Elodea" fields based on what you observed from each experimental setup.
The "Independent Variable" and "Identify the Dependent" fields ask you to name what changes between setups (the combination of organisms) and what you measure as the outcome (the color change of the indicator solution).
Finalize the results table by recording Test Tube labels, Independent Variables, Beginning Color, Color Prediction, and Color Result for each of the four setups: control (no organisms), snails only, Elodea only, and snails plus Elodea together.
Step 3: When you have completed all sections, click the "Done" button to download or save your finished worksheet.
Step 4: Save at least two copies of the completed lab form for your records.
Related Biology Worksheets
For additional biology practice on related topics, explore the Photosynthesis Diagrams Worksheet or the Laboratory Skills Assessment Worksheet on FormsPal. The Regents Biology Lab on Food Chains covers similar ecosystem concepts about producers and consumers.
Common Questions About the Lab Worksheet
What does Bromthymol Blue indicate in this experiment?
Bromthymol Blue changes color based on the amount of CO2 dissolved in the water. It turns yellow when carbon dioxide is present and stays blue or green when CO2 levels are low.
What are the independent and dependent variables?
The independent variable is the combination of organisms placed in each test tube (control, snails only, Elodea only, or both). The dependent variable is the color of the Bromthymol Blue solution after the experiment, which reflects whether CO2 increased or decreased in that tube.
What conclusion do students draw from the lab?
Students conclude that snails raise CO2 levels through cellular respiration, while Elodea lowers CO2 through photosynthesis. In tubes containing both organisms, the CO2 level depends on which process is more active, shown by the indicator color at the end of the experiment.
